Physics 194 Exam 1 Question And Answers, COMPLETE SOLUTIONS
2021/2022.
Exam 1 solutions 2022 Physics 194
Name:
Instructions:
Score
The responsibility is yours to show me that you understand what you are doing so please
1:
show all your work. If you feel you are stuck on a particular part explain as much of your
thinking as you can so I can give you the maximum amount of partial credit (explain the 2:
strategy you are using, draw pictures/graphs, etc.)
3:
Use the backs of the exam pages if you need extra space.
4:
Each problem is worth 10 points. The problems are not all of the same difficulty though, so
5:
budget your time wisely.
Total
The last pages of the exam contain useful physical constants, conversion factors, and other
data. Please check there first if you feel you need more information than is given in the
problem.
/50
Good luck!
1. Two identical light bulbs are connected in series to a
power supply as shown. Your friend says the 120V
following: “Bulb #1 will be brighter than bulb #2 since
it is closer to the positive terminal of the battery and
the charges have more energy there.” You don’t think
this sounds right…
a. Explain what is wrong with your friend’s
R2 108 R1 108
reasoning. Give you own improved energy-based
explanation.
b. Determine the power output of each bulb.
The brightness of a light bulb depends on how much electric potential energy is transformed
into internal energy in the light bulb. That means it’s about how much the energy of the charges
decreases by, not how much they have when they reach the bulb. Since the two light bulbs are
identical and are in series, charges will lose the same amount of energy going through each one.
As a result, they will have the same brightness.
One way to determine the power output of each bulb is to first determine the current through
them. I’ll use Kirchhoff’s loop rule, starting at the negative terminal of the power supply and
traversing the loop clockwise
V 0
V VR VR 0
1 2
IR1 IR2 0
120V 0.556 A
I 108 108
R R
, Physics 194 Exam 1 Question And Answers, COMPLETE SOLUTIONS
2021/2022.
1 2
2021/2022.
Exam 1 solutions 2022 Physics 194
Name:
Instructions:
Score
The responsibility is yours to show me that you understand what you are doing so please
1:
show all your work. If you feel you are stuck on a particular part explain as much of your
thinking as you can so I can give you the maximum amount of partial credit (explain the 2:
strategy you are using, draw pictures/graphs, etc.)
3:
Use the backs of the exam pages if you need extra space.
4:
Each problem is worth 10 points. The problems are not all of the same difficulty though, so
5:
budget your time wisely.
Total
The last pages of the exam contain useful physical constants, conversion factors, and other
data. Please check there first if you feel you need more information than is given in the
problem.
/50
Good luck!
1. Two identical light bulbs are connected in series to a
power supply as shown. Your friend says the 120V
following: “Bulb #1 will be brighter than bulb #2 since
it is closer to the positive terminal of the battery and
the charges have more energy there.” You don’t think
this sounds right…
a. Explain what is wrong with your friend’s
R2 108 R1 108
reasoning. Give you own improved energy-based
explanation.
b. Determine the power output of each bulb.
The brightness of a light bulb depends on how much electric potential energy is transformed
into internal energy in the light bulb. That means it’s about how much the energy of the charges
decreases by, not how much they have when they reach the bulb. Since the two light bulbs are
identical and are in series, charges will lose the same amount of energy going through each one.
As a result, they will have the same brightness.
One way to determine the power output of each bulb is to first determine the current through
them. I’ll use Kirchhoff’s loop rule, starting at the negative terminal of the power supply and
traversing the loop clockwise
V 0
V VR VR 0
1 2
IR1 IR2 0
120V 0.556 A
I 108 108
R R
, Physics 194 Exam 1 Question And Answers, COMPLETE SOLUTIONS
2021/2022.
1 2
